How would you guys validate user data from a simple login/signup form that has email, password and maybe name fields, using a form. On nodejs, you could use express-validator, but that is server sided, how would I have the same mechanism in electron?
Or could I send request to a server and validate there and bring back errors to the user?

Electron can do all of the normal Node things. I don’t know if express-validator is reliant on other parts of Express or not, but if it’s not, then it should be usable. If not, it’s really not difficult to write a validation algorithm in JavaScript.

You’re still looking at express-validator and you shouldn’t be. It’s designed to serve a specific purpose for a web server package, express. What you want to write your validator is to require validator and use its functions to check input.